Process of manufacturing screw taps or similar thread-cutting tools



' C. DEBROT iROCESS OF MANUFACTURING SCREW TAPS. 0R SIMILAR THREAD CUTTING TOOLS Filed Oct. 21, 1922 pa t Feh.1 0, 1925. H

UNITED STATES CHARLES DEBROT, OF BELLE, FRANCE, ASSIGNOB T SOGIIE'JJE INDUSTRIELLE DE BELLE, OF DELLE, TERRITOIRE DE BELFORT, FRANCE, A LIMITED JOINT STOCK COMPANY OF FRANCE.

QROCESS OF MANUFACTURING SCREW TAPS OR SIMILAR THREAD-CUTTING TOOLS.

Application filed October 21, 1922. Serial No. 595,908.

To all whom it may concern: Be it known that I, CHARLES DEBRo'r, citizen of the Republic of France, residing at Delle, Territoire de Belfort, France, have i invented certain new and useful Improvements in Processes ofManufacturing Screw Taps or Similar Thread-Cutting Tools, of which the following is a specification.

My invention has reference to screw-taps and the like, and my present invention con sists in a new process of manufacturing screw-taps, and similar thread-cuttingtools.

Inthe accompanying drawing,

Fig. 1 is anelevation of a screw tap in accordance with this invention.

Fig. 2 is a section of said screw tap on line 2-2 of Fig. 1.

Fig. 3 is an elevation of a cutter used in t a special process of manufacture which also forms part of this invention.

Fig. 4 is a section of saidcutter on line 4-4 of Fig. 3. a Fig. 5 is a diagrammatic partial development'of the surface of a screw tap made by said process.

The screw-tap as shown in Figs. 1 and 2 comprises a first working portion 1 havinga slightlyconical outline and provided with a few teeth 2 having shallow faces; a second working portion 3 is provided with an interrupted set of teeth, that is, a series of teeth asin the ordinary screw taps, except that one tooth out of. every two is omitted: a third working portion 4 shows a seriesof teeth of normal outline.

Three longitudinal grooves 5 produce, in a well-known manner. three toothed zones 6 with acutting edge 7.

The invention now consists in a new to process of producing in a particular precise v manner the interrupted series of teeth, that i is the portion 3 of the tap.

This new process which makes it possible to obtain in a simple mannerland with great i i accuracy,screw taps with alternate or discontinuous teeth, consists essentially first in threading the shank at t escrow tap inthe usual way to the pitch the discriminant-2s teeth it is desired to obtain, and then by a reverse helical out half the original thread is removed so as to leave a helical strip or portion and when the usual longitudinal grooves are cut in'the shank to finish the screw tap theremaining intact/portions of the original thread in one toothed zone will alternate with the intact portions in the next zone.

The operation may be carried out as follows a On a cutting machine is fitted a cutter 10 (Figs. 3 and 4:) the truncation of which, i. e. the distance the edges '12 and 13, is equal to the pitch of the screw-tap to be formed. Said cutter is displaced in a direction opposite to the pitch of the threads and proportionally to the number of edges of the screw-tap so as to cross the pitch as many times as there are divisions in the screw tap.

In the course of said motion, the cutter cuts on the screw-tap a groove 14 as shown in the diagrammatic view, Fig. 5, which is such that each thread 15 is almost entirely removed by the cutting of the groove 14 in the division 16 of the screw-tap, excepting a few out portions such as 17. thread is slightly torn off in the division 18 and is not touched in the division 19. It is therefore suificient, after cutting the groove 14 to remove the cut portions such as 17 and to make the longitudinal cuts in one division out of two, as for instance, in division 18, and a screw-tap partly toothed only is thus obtained.

Claims:

1. The method of producing screw taps or similar thread cutting tools having interrupted teeth, which consists in first threading in the usual way the shank of the screw tap tothe pitch of the interrupted thread it is desired to obtain, then cutting this screw tap along a groove in the reverse direction of the threads of the screw tap, the said groove being" inclined atar'r' ange, so as to remove one teeth out of tee in the toothed1 'zone's provided between the usu-ai The same longitudinal cuts of the tap, and finally finthe said cutter being at the same time given ishing the tap by producing therein said a rotary movement about its axis and a longitudinal cuts. travelling movement parallel to the axis of 10 2. The method as specified in claim 1, in the tap in the reverse direction relative to 5 which the said inclined groove is cut by the pitch of the tap.

means of a cutter having a truncation equal In testimony whereof I aflix my signature. to the, sizjeof the screw-threads of the tap, GHARLESDEBBOT. 

